Effective treatment with IDH inhibitors, cytotoxic therapy, or vaccine therapy should result in decreased 2HG levels,26,27 with more rapid decreases in oligodendrogliomas than in astrocytomas, possibly related to their increased chemosensitivity.26,28 The 2HG MRS is therefore a promising noninvasive metabolic imaging biomarker that can aid the imaging diagnosis of IDH-mutant gliomas versus IDH-wildtype gliomas and other non-glioma tumors, as well as inform clinical management decisions during treatment. The gene discussed is IDH1; the disease is astrocytoma (excluding glioblastoma).